New Zealand's birds are facing a real threat of extinction, with many populations on the verge of blinking out due to exploding predator numbers.Right now we're witnessing the biggest aerial drop of 1080 in our history. They're dropping poison on around 700,000 hectares of the country.Of course there are plenty of people who think there's a better way to control pests.

Sam Hayes went bush with the Department of Conservation to find out all about this massive 1080 operation, whether it's really necessary and what the alternatives might be.

"We think of New Zealand as being this gem of wildlife stuff; it's not," says Graeme Elliot from the Department of Conservation. "New Zealand's a desert. Most of the great stuff we had, we've lost. Our forests are quiet because the birds in them have been eaten by stoats and rats. If we want our forest to be noisy, if we want kokako and kaka, we have to control stoats and rats and we have to do it on a big scale."When Mr Elliot talks about doing something "on a big scale", he means this year's Department of Conservation Battle for Our Birds – the largest ever aerial drop of 1080 poison into our forests. Without it, the department says, 2014 could go down in history as the year we lost our birds forever.Department of Conservation is shooting branches off southern beeches in order to count their seeds, because 2014 is what's called a mast year – when our beech forests produce a bonanza crop of seeds. That means a bumper food source for rats and stoats. Predator populations explode, and then they turn on the birds.The obvious objection to 1080 is that it is a poison, and with every aerial drop, there's a risk of killing some of the very birds the Department of Conservation is trying to save, something Mr Elliot reluctantly accepts.But it seems we could soon have a new weapon in the war against predators. Researcher Janine Duckworth has been developing a real alternative in Christchurch – a contraceptive vaccine specifically for possums.Injected into the animal, it has an up to 80 percent success rate in rendering possums sterile, effectively destroying some populations. All that remains is to find a way to feed it to them. But like so many promising scientific projects, there’s a familiar catch – lack of funding.Until those pieces come together, the Department of Conservation says the battle is reliant on existing predator control tools. Last week we went back to Westland's Maruia forest to look at whether the tracking tunnels show any change in rat and mouse populations after the 1080 drop.Watch the video for the full report.Credits: